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  • 1
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    Organic Matter in the Surface Microlayer: Insights From a Wind Wave Channel Experiment (2018)
    Frontiers
    In:  Frontiers in Marine Science, 5 . Art.Nr. 182.
    Details
    Publication Date: 2021-03-18
    Description: The surface microlayer (SML) is the uppermost thin layer of the ocean and influencing interactions between the air and sea, such as gas exchange, atmospheric deposition and aerosol emission. Organic matter (OM) plays a key role in air-sea exchange processes, but studying how the accumulation of organic compounds in the SML relates to biological processes is impeded in the field by a changing physical environment, in particular wind speed and wave breaking. Here, we studied OM dynamics in the SML under controlled physical conditions in a large annular wind wave channel, filled with natural seawater, over a period of 26 days. Biology in both SML and bulk water was dominated by bacterioneuston and -plankton, respectively, while autotrophic biomass in the two compartments was very low. In general, SML thickness was related to the concentration of dissolved organic carbon (DOC) but not to enrichment of DOC or of specific OM components in the SML. Pronounced changes in OM enrichment and molecular composition were observed in the course of the study and correlated significantly to bacterial abundance. Thereby, hydrolysable amino acids, in particular arginine, were more enriched in the SML than combined carbohydrates. Amino acid composition indicated that less degraded OM accumulated preferentially in the SML. A strong correlation was established between the amount of surfactants coverage and γ-aminobutric acid, suggesting that microbial cycling of amino acids can control physiochemical traits of the SML. Our study shows that accumulation and cycling of OM in the SML can occur independently of recent autotrophic production, indicating a widespread biogenic control of process across the air-sea exchange.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3389/fmars.2018.00182
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Using cavity ringdown spectroscopy for continuous monitoring of δ13C(CO2) and ƒCO2 in the surface ocean (2012)
    American Society of Limnology and Oceanography
    In:  Limnology and Oceanography: Methods, 10 . pp. 752-766.
    Details
    Publication Date: 2019-09-23
    Description: The role of the global surface ocean as a source and sink for atmospheric carbon dioxide and the flux strengths between the ocean and the atmosphere can be quantified by measuring the fugacity of CO2 (ƒCO2) as well as the dissolved inorganic carbon (DIC) concentration and its isotopic composition in surface seawater. In this work, the potential of continuous wave cavity ringdown spectroscopy (cw-CRDS) for autonomous underway measurements of ƒCO2 and the stable carbon isotope ratio of DIC [δ13C(DIC)] is explored. For the first time, by using a conventional air-sea equilibrator setup, both quantities were continuously and simultaneously recorded during a field deployment on two research cruises following meridional transects across the Atlantic Ocean (Bremerhaven, Germany–Punta Arenas, Chile). Data are compared against reference measurements by an established underway CO2 monitoring system and isotope ratio mass spectrometric analysis of individual water samples. Agreement within ΔƒCO2 = 0.35 μatm for atmospheric and ΔƒCO2 = 2.5 μatm and Δδ13C(DIC) =0.33‰ for seawater measurements have been achieved. Whereas “calibration-free” ƒCO2 monitoring is feasible, the measurement of accurate isotope ratios relies on running reference standards on a daily basis. Overall, the installed CRDS/equilibrator system was shown to be capable of reliable online monitoring of ƒCO2, equilibrium δ13C(CO2), δ13C(DIC), and pO2 aboard moving research vessels, thus making possible corresponding measurements with high spatial and temporal resolution.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.4319/lom.2012.10.752
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Design and field application of a UV-LED based optical fiber biofilm sensor (2012)
    Elsevier
    In:  Biosensors and Bioelectronics, 33 (1). pp. 172-178.
    Details
    Publication Date: 2019-09-23
    Description: Detecting changes in the formation dynamics of biofilms stemming from bacteria and unicellular microorganisms in their natural environment is of prime interest for biological, ecological as well as anti-fouling technology research. We developed a robust optical fiber-based biofilm sensor ready to be applied in natural aquatic environments for on-line, in situ and non-destructive monitoring of large-area biofilms. The device is based on the detection of the natural fluorescence of microorganisms constituting the biofilm. Basically, the intrinsic fluorescence of the amino acid tryptophan is excited at a wavelength of λ=280 nm and detected at λ=350 nm utilising a numerically optimized sensor head equipped with a UV-LED light source and optical fiber bundles for efficient fluorescence light collection. Calibration was carried out with tryptophan solutions and two characteristic marine bacteria strains revealing linear signal response, satisfactory background suppression, wide dynamic range, and an experimental detection limit of 4 × 10(3)cells/cm(2). Successful field experiments in the Baltic Sea accomplished over a period of twenty-one days provided for the first time continuous observation of biofilm formation dynamics in a natural habitat. Starting from the first adhering bacteria, the measurement yielded the characteristic three phases of biofilm formation up to a fully developed biofilm. The sensor system holds potential for applications in aquatic sciences including deep sea research and, after further miniaturisation, in the industrial and biomedical field.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.bios.2011.12.048
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Seasonal signatures in SFG vibrational spectra of the sea surface nanolayer at Boknis Eck Time Series Station (SW Baltic Sea) (2013)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 10 . pp. 5325-5334.
    Details
    Publication Date: 2019-09-23
    Description: The very thin sea surface nanolayer on top of the sea surface microlayer, sometimes just one monomolecular layer thick, forms the interface between ocean and atmosphere. Due to the small dimension and tiny amount of substance, knowledge about the development of the layer in the course of the year is scarce. In this work, the sea surface nanolayer at Boknis Eck Time Series Station (BE), southwestern Baltic Sea, has been investigated over a period of three and a half years. Surface water samples were taken monthly by screen sampling and were analyzed in terms of organic content and composition by sum frequency generation spectroscopy, which is specifically sensitive to interfacial layers. A yearly periodicity has been observed with a pronounced abundance of sea surface nanolayer material(such as carbohydrate-rich material) during the summer months. On the basis of our results we conclude that the abundance of organic material in the nanolayer at Boknis Eck is not directly related to phytoplankton abundance alone. We speculate that indeed sloppy feeding of zooplankton together with photochemical and/or microbial processing of organic precursor compounds is responsible for the pronounced seasonality.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/bg-10-5325-2013
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Fluorescence-Based Quasicontinuous and In Situ Monitoring of Biofilm Formation Dynamics in Natural Marine Environments (2014)
    American Society for Microbiology
    In:  Applied and Environmental Microbiology, 80 (12). pp. 3721-3728.
    Details
    Publication Date: 2019-09-23
    Description: Analyzing the dynamics of biofilm formation helps to deepen our understanding of surface colonization in natural environments. While methods for screening biofilm formation in the laboratory are well established, studies in marine environments have so far been based upon destructive analysis of individual samples and provide only discontinuous snapshots of biofilm establishment. In order to explore the development of biofilm over time and under various biotic and abiotic conditions, we applied a recently developed optical biofilm sensor to quasicontinuously analyze marine biofilm dynamics in situ. Using this technique in combination with microscope-assisted imaging, we investigated biofilm formation from its beginning to mature multispecies biofilms. In contrast to laboratory studies on biofilm formation, a smooth transition from initial attachment to colony formation and exponential growth could not be observed in the marine environment. Instead, initial attachment was followed by an adaptation phase of low growth and homogeneously distributed solitary bacterial cells. Moreover, we observed a diurnal variation of biofilm signal intensity, suggesting a transient state of biofilm formation of bacteria. Overall, the biofilm formation dynamics could be modeled by three consecutive development stages attributed to initial bacterial attachment, bacterial growth, and attachment and growth of unicellular eukaryotic microorganisms. Additional experiments showed that the presence of seaweed considerably shortened the adaptation phase in comparison with that on control surfaces but yielded similar growth rates. The outlined examples highlight the advantages of a quasicontinuous in situ detection that enabled, for the first time, the exploration of the initial attachment phase and the diurnal variation during biofilm formation in natural ecosystems
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1128/AEM.00298-14
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Toward continuous monitoring of seawater 13CO2/12CO2 isotope ratio and pCO2: Performance of cavity ringdown spectroscopy and gas matrix effects (2010)
    American Society of Limnology and Oceanography
    In:  Limnology and Oceanography: Methods, 8 . pp. 539-551.
    Details
    Publication Date: 2019-09-23
    Description: The potential of a continuous wave cavity ringdown spectrometer for monitoring the isotope ratio 13CO2/12CO2 and the partial pressure pCO2 of CO2 dissolved in water was thoroughly analyzed by quantitative measurements. Running calibration gas standards under typical operation conditions, a relative accuracy of D(d13C[CO2]) = ±0.1‰ with 120 min averaging time has been demonstrated. Absolute uncertainties were determined to be D(d13C[CO2]) = ±0.2‰ and D(xCO2) = ±0.5 ppmv. No principle problems were encountered when using the instrument in combination with a water-air equilibration setup. By contrast, when performing measurements of CO2 in gas matrices with a composition different from that of ambient air, pressure broadening linewidth effects induced significant errors in both d13C(CO2) and xCO2 values. These effects, which compromise the accessible accuracy in environmental studies, can be quantitatively taken into account by using a spectroscopically based correction procedure. Relying on linewidth analysis, the instrument was shown to be capable of continuous and simultaneous measurement of d13C(CO2), pCO2, as well as water content and O2 supersaturation, and thus holds the potential for online monitoring of these quantities aboard research vessels.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.4319/lom.2010.8.539
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Enhanced CRDS Methods for Trace Gas Detection and Surface Analysis (2013)
    In:  [Poster] In: Clusterretreat Future Ocean, 09.-10.09.2013, Schleswig, Germany .
    Details
    Publication Date: 2019-09-23
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Poster
  • 8
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    Design and field application of an optical fiber biofilm sensor (2011)
    In:  [Talk] In: 1. International Conference on Marine Resources and Beyond, 05.-07.09.2011, Bremerhaven, Germany .
    Details
    Publication Date: 2019-09-23
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Talk
  • 9
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    CRDS Based Field Measurements of Surface Water pCO2 and δ13C(CO2) on two Atlantic Transects (2010)
    In:  [Poster] In: 3. Biannual Symposium "Future Ocean", 13.-16.09.2010, Kiel, Germany .
    Details
    Publication Date: 2019-09-23
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Poster
  • 10
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    Methodological Issues of CRDS Based Underway Monitoring of Surface Ocean d13C(CO2) (2012)
    In:  [Poster] In: SOLAS Open Science Conference, 07. - 10.05.2012, Cle Elum, Washington, USA .
    Details
    Publication Date: 2019-09-23
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Poster
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